Introduction: Critically ill children in the pediatric intensive care unit (PICU) are at high risk for developing nutritional deficiencies and undernutrition is known to be a risk factor for morbidity and mortality. Malnutrition represents a continuous spectrum ranging from marginal nutrient status to severe metabolic and functional alterations and this in turn, affects clinical outcome. Objectives: The aim of the study was to assess nutritional status of critically ill children admitted to the PICU and its association to clinical outcomes. Methods: Critically ill children age 6 months to 18 years were prospectively enrolled on PICU admission. Nutritional status was assessed by weight for age (WFA: underweight), weight for height (WFH: wasting), height for age (HFA: stunting) z-scores and mid upper arm circumference (MUAC: wasting) according to the WHO. (1,2) Malnutrition was defined as mild, moderate, and severe if z-scores were > −1, > − 2, and > −3, respectively. Hospital and PICU length of stay (LOS), duration of mechanical ventilation (MV), and risk of mortality (ROM) by the Pediatric Index of Mortality 2 (PIM2) were obtained. Sensitivity and specificity of the MUAC to identify children with wasting (WFH) were calculated. Results: Two hundred and fifty children (136 males), aged 81 months (23-167; median (25-75 th IQR)), were prospectively included in the study. The hospital LOS was 8 (4-16) days; PICU LOS: 2 (1-4) days; duration of MV, 0 (0-1.5) days;